Hongli Lai, co-founder of Phusion and Passenger engineer, shares his quest for an easy-to-use monitoring solution for Phusion's servers.
Unlike the other solutions I've checked out, Netdata provides real-time, per-second monitoring. You can see the CPU/memory slider update in real time. Netdata also provides alerting and installs a ton of alerts by default. By default Netdata stores collected stats on the same server. This is very convenient if you are just getting started. It can also be configured to send stats to a central server.
Also, go back in time to 2015 when we talked with Hongli on The Changelog #136.